hyperv: avoid query memleaks on failure

The function hypervEnumAndPull consumes query on success, but leaked
it on failure.  Rather than having to change all callers (many of
them indirect callers through the generated
hypervGetMsvmComputerSystemList), it was easier to just guarantee
that the buffer is cleaned on return from the function.

* src/hyperv/hyperv_wmi.c (hypervEnumAndPull): Don't leak query on
failure.
Signed-off-by: NEric Blake <eblake@redhat.com>

src/hyperv/hyperv_wmi.c

@@ -2,6 +2,7 @@
  * hyperv_wmi.c: general WMI over WSMAN related functions and structures for
  *               managing Microsoft Hyper-V hosts
  *
+ * Copyright (C) 2014 Red Hat, Inc.
  * Copyright (C) 2011 Matthias Bolte <matthias.bolte@googlemail.com>
  * Copyright (C) 2009 Michael Sievers <msievers83@googlemail.com>
  *
@@ -105,6 +106,7 @@ hyperyVerifyResponse(WsManClient *client, WsXmlDocH response,
  * Object
  */
 
+/* This function guarantees that query is freed, even on failure */
 int
 hypervEnumAndPull(hypervPrivate *priv, virBufferPtr query, const char *root,
                   XmlSerializerInfo *serializerInfo, const char *resourceUri,
@@ -123,13 +125,17 @@ hypervEnumAndPull(hypervPrivate *priv, virBufferPtr query, const char *root,
     XML_TYPE_PTR data = NULL;
     hypervObject *object;
 
-    if (list == NULL || *list != NULL) {
-        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Invalid argument"));
+    if (virBufferCheckError(query) < 0) {
+        virBufferFreeAndReset(query);
         return -1;
     }
+    query_string = virBufferContentAndReset(query);
 
-    if (virBufferCheckError(query) < 0)
+    if (list == NULL || *list != NULL) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("Invalid argument"));
+        VIR_FREE(query_string);
         return -1;
+    }
 
     serializerContext = wsmc_get_serialization_context(priv->client);
 
@@ -141,7 +147,6 @@ hypervEnumAndPull(hypervPrivate *priv, virBufferPtr query, const char *root,
         goto cleanup;
     }
 
-    query_string = virBufferContentAndReset(query);
     filter = filter_create_simple(WSM_WQL_FILTER_DIALECT, query_string);
 
     if (filter == NULL) {